FIG. 1 illustrates the configuration of a conventional signal processing circuit in a single plate-type CCD color camera.
A first 1H delay circuit 1 generates a video signal obtained by delaying an input video signal (a CCD output signal) by 1H (one horizontal period). A second 1H delay circuit 2 generates a video signal obtained by further delaying by 1H the video signal delayed by 1H.
The input video signal, the video signal delayed by 1H, and the signal delayed by 2H are fed to a YC separating circuit 3. A luminance signal Yh, a vertical contour signal Vap, a G signal, an R signal, and a B signal are outputted from the YC separating circuit 3.
The luminance signal Yh and the vertical contour signal Vap are fed to a Y process circuit 4, are subjected to predetermined luminance signal processing, and are then outputted as a luminance signal Yout.
The G signal, the R signal, and the B signal are fed to a color difference matrix circuit 5. The color difference matrix circuit 5 comprises four adders 11, 12, 13, and 14, four multipliers 21, 22, 23, and 24, and a color difference matrix coefficient register 25 for giving a multiplication coefficient to each of the multipliers 21, 22, 23, and 24. The multiplication coefficient given to each of the multipliers 21, 22, 23, and 24 is set in the color difference matrix coefficient register 25 by a CPU 7.
Letting KRRY, KRBY, KBRY, and KBBY be respectively the multiplication coefficients given to the multipliers 21, 22, 23, and 24, the color difference matrix circuit 5 performs an operation expressed by the following equation (1), to generate color difference signals (R−Y) and (B−Y).R−Y=KRRY(R−G)+KBRY(B−G)B−Y=KRBY(R−G)+KBBY(B−G)  (1)
The color difference signals (R−Y) and (B−Y) obtained by the color difference matrix circuit 5 are fed to a color encoding circuit 6.
In the color encoding circuit 6, two color carriers between which there is a phase difference of 90 degrees are respectively modulated by the color difference signals (R−Y) and (B−Y), and are synthesized, to generate a chrominance signal Cout.
In the above-mentioned circuit, the tone of a video output can be adjusted by changing the coefficients KRRY, KRBY, KBRY, and KBBY in the color difference matrix circuit 5. That is, a gain in an R−Y direction, a hue (HUE) corresponding to a B−Y axis, a hue (HUE) corresponding to an R−Y axis, and a gain in a B−Y direction are respectively adjusted by the coefficients KRRY, KBRY, KRBY, and KBBY, as shown in FIGS. 2a, 2b, 2c, and 2d. 
Meanwhile, in the case of the single plate type CCD color camera, a color filter is arranged on a front surface of a CCD. Particularly when a complementary color filter is used as the color filter, it is difficult to change the spectral-response characteristics of Ye, Mg, Cy, and G color filters to ideal characteristics. Accordingly, a color different from the inherent color is reproduced.
For example, green-based colors are not easily obtained, blue-based colors are predominantly obtained, and red-based colors are shifted in a magenta direction. It is difficult to adjust such degradation of color reproducibility only by the coefficients KRRY, KRBY, KBRY, and KBBY in the color difference matrix circuit 5. The reason for this is that in a case where green-based colors are insufficient, for example, when the coefficient KRRY is increased, green can be heightened, while cyan, red, and magenta are also similarly heightened.
An object of the present invention is to provide a tone correcting circuit capable of correcting a tone only for an arbitrary hue.
Another object of the present invention is to provide a hue correcting circuit capable of correcting a hue only for an arbitrary hue.
Still another object of the present invention is to provide a color correcting circuit capable of correcting a color only for a hue within an arbitrary range out of all hue ranges.